KENNEDY SPACE CENTER, FLA. - Space Shuttle Discovery, atop its Mobile Launcher Platform and Crawler/Transporter, inches its way back to NASA?s Vehicle Assembly Building (VAB) at Kennedy Space Center. Rolling back from Launch Pad 39B, it is passing alongside the turn basin near the VAB. Once inside the VAB, Discovery will be demated from its External Tank and lifted into the transfer aisle. On or about June 7, Discovery will be lifted and attached to its new tank and Solid Rocket Boosters, which are already in the VAB. Only the 15th rollback in Space Shuttle Program history, the 4.2-mile journey allows additional modifications to be made to the External Tank prior to a safe Return to Flight. Discovery is expected to be rolled back to the launch pad in mid-June for Return to Flight mission STS-114. The launch window extends from July 13 to July 31.